Alumina coating on dense tungsten powder by fluidized bed metal organic chemical vapour deposition

In order to study the feasibility of coating very dense powders by alumina using Fluidized Bed Metal Organic Chemical Vapour Deposition (FB-MOCVD), experiments were performed on a commercial tungsten powder, 75 microm in median volume diameter and 19,300 kg/m3 in grain density. The first part of the work was dedicated to the experimental study of the tungsten powder fluidization using argon as carrier gas at room temperature and at 400 degrees C. Due to the very high density of the tungsten powder, leading to low initial fixed bed heights and low bed expansions, different weights of powder were tested in order to reach satisfactory temperature profiles along the fluidized bed. Then, using argon as a fluidized bed former and aluminium acetylacetonate Al(C5O2H7)3 as a single source precursor, alumina thin films were deposited on tungsten particles at a low temperature range (e.g., 370-420 degrees C) by FB-MOCVD. The influence of the weight of powder, bed temperature and run duration was studied. Characterizations of the obtained samples were performed by various techniques including scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) analyses, Field Emission Gun SEM (FEG-SEM) and Fourier Transform InfraRed (FT-IR) spectroscopy. The different analyses indicated that tungsten particles were uniformly coated by a continuous alumina thin film. The thickness of the film ranged between 25 and 80 nm, depending on the coating conditions. The alumina thin films were amorphous and contained carbon contamination. This latter may correspond to the adsorption of species resulting from incomplete decomposition of the precursor at so low deposition temperature.     

Biomass production and small-scale testing of freeze-dried lactic acid bacteria starter strains for cassava fermentations

Based on their predominance in Gari fermentations, as well as suitable technological properties, Lactobacillus plantarum, Lactobacillus fermentum, Weissella paramesenteroides and Leuconostoc mesenteroides strains were investigated for their suitability for development as starter strains for this African traditional fermented cassava product. The strains were grown in optimized growth media in 2 L fermenters, harvested and freeze dried, and then tested in lab-scale cassava mash fermentation trials for their ability to ferment the cassava. The strains performed well and rapidly increased the titratable acidity from 1.1 to 1.3% at 24 h to 1.3–1.6% at 48 h. The benefit of including starter cultures was that it lowered the pH of the product much faster and to lower levels than in the uninoculated control fermentation. The results furthermore indicated that especially the L. plantarum-group strains could be produced as starter strains at low cost. Overall, the results of this study showed that starter strains could be easily and economically produced, and thus represent a feasible possibility for further development for application in the field.     

A Bifunctional Copper Catalyst for the One Pot-One Step Esterification?+?Hydrogenation of Tall Oil Fatty Acids

An efficient copper catalyst for the one-pot one-step hydrogenation?+?esterification of unsaturated free fatty acids is described. The high selectivity in hydrogenation promoted by copper, combined with the high activity in esterification observed with solid mixed oxides allows one to directly obtain stabilized methyl esters.     

Photopolymerization of N,N-Didodecyl- N-methyl-N-ethylmethacrylate ammonium chloride,a reverse micelle forming surfactant

A detailed study of the photopolymerization of N,N-didodecylmethylethylmethacrylate ammonium chloride, a reverse micelle forming surfactant, is presented. The polymerization was photochemically initiated at 350 nm using AIBN and p-AIBN as initiators. However, the polymerization could also be initiated through direct excitation of the methacrylate group. High rates of polymerization resulted because of the organization of the monomer in reverse micellar assemblies. The molecular weights of the polymer decrease with increasing initiator concentration and are always larger than the molecular weight of the reverse micelle. The properties of the monomeric reverse micellar system are compared with those of the polymeric system and show that the dynamic character of the reverse micellar system can be lowered upon polymerization. The properties of the polymeric aggregates, however, differ if a given amount of water is solubilized before or after polymerization. The mean aggregation number of the monomeric and polymeric aggregates as well as the aggregation behaviour of both systems are compared. This comparison suggests that a polymeric aggregate consists of more than one polymer chain.     

State estimation for large-scale wastewater treatment plants

Many relevant process states in wastewater treatment are not measurable, or their measurements are subject to considerable uncertainty. This poses a serious problem for process monitoring and control. Model-based state estimation can provide estimates of the unknown states and increase the reliability of measurements. In this paper, an integrated approach is presented for the optimization-based sensor network design and the estimation problem. Using the ASM1 model in the reference scenario BSM1, a cost-optimal sensor network is designed and the prominent estimators EKF and MHE are evaluated. Very good estimation results for the system comprising 78 states are found requiring sensor networks of only moderate complexity.     

The Impact of Iron Oxide Concentration on the Performance of Molten Oxide Electrolytes for the Production of Liquid Iron Metal

Metallurgical and Materials Transactions B - The effect of iron oxide concentration on the conductive behavior of a molten oxide electrolyte has been investigated at 1823 K using stepped...     

Fault detection and identification relying on set-membership identifiability

Identifiability is the property that a mathematical model must satisfy to guarantee an unambiguous mapping between its parameters and the output trajectories. It is of prime importance when parameters must be estimated from experimental data representing input–output behavior and clearly when parameter estimation is used for fault detection and identification. Definitions of identifiability and methods for checking this property for linear and nonlinear systems are now well established and, interestingly, some scarce works (Braems et al., 2001, Jauberthie et al., 2011) have provided identifiability definitions and numerical tests in a bounded-error context. This paper resumes and better formalizes the two complementary definitions of set-membership identifiability and μ-set-membership identifiability of Jauberthie et al. (2011) and presents a method applicable to nonlinear systems for checking them. This method is based on differential algebra and makes use of relations linking the observations, the inputs and the unknown parameters of the system. Using these results, a method for fault detection and identification is proposed. The relations mentioned above are used to estimate the uncertain parameters of the model. By building the parameter estimation scheme on the analysis of identifiability, the solution set is guaranteed to reduce to one connected set, avoiding this way the pessimism of classical set-membership estimation methods. Fault detection and identification are performed at once by checking the estimated values against the parameter nominal ranges. The method is illustrated with an example describing the capacity of a macrophage mannose receptor to endocytose a specific soluble macromolecule.     

Influence of powder characteristics on the behaviour of PIM feedstock

This work aims to analyse the impact of powders which are not conventionally intended for powder injection moulding (PIM) and how their characteristics influence the behaviour of the feedstock during mixing. Tests were performed with different alumina powders using the same binder system. The results show that mixing has a strong impact on the packing density of powders inside the feedstock, while the deagglomeration of powders makes it possible to achieve high critical powder volume concentrations (CPVCs) equal to or greater than 58 vol%. The CPVC depends on the deagglomeration efficiency. The agglomeration state – especially cohesion of the agglomerates – has an influence on the CPVC. The comparative study of mixing torques shows that the grain size and surface area of powders have a major impact on the mixing behaviour of the feedstock. During the implementation of powders, variabilities in the homogenisation of the powder/binder system and in deagglomeration are achieved as a result of powder agglomeration. It was demonstrated that the powders in this study perfectly satisfy the criteria imposed by the mixing process although they are not intended for PIM.     

更携式医疗设备中的信号调整

现今的医疗便携设备方便病人自行诊疗、自由走动,甚至可在外出时使用设备。便携式电子医疗设备要实现“方便携带”的特色功能,就必须具备微型化和低功耗的特性。此外,这些设备还要有极高的精度以确保病人的安全。医疗设备采用多种不同的传感器来龄视病人的健康状况,然后传感器将生理信号转换成电子信号供电子设备分析使用。由于医疗设备中传输的信号都比较微弱,而且还会受到诸多噪声源的干扰,因此信号路径设计对便携式医疗设备就显得格外重要了。本文将针对心电图机和血糖测量仪这两种设备应用,讨论如何将传感器与匹配的PowerWise放大器相连接,以便延长电池寿命和提高诊疗安全性。